Electric power system



June 15, 1937. E. F. w. ALExANDr-:RsoN ET AL 2,084,177

ELECTRIC POWER SYSTEM Filed Feb. 29, 1936 5 SheetS-Sheet l SPL-fo avr/f Hara/rs runs) SPEED REVE/FSE Inventors: Ernest FT W. Alexandersn,

wi Albert H-Mitta y "g Tha/W/ June 15, 1937. E. F, w. ALExANDERsoN ET AL 2,084,177'

ELECTRIC POWER SYSTEM Filed Feb'. 29, 1936 I5 Sheets-Sheet 2 Albert H. Mittag,

Their Attorr'wey.

v F/lglla.

June 15, 1937. E. F. w. ALExANDERsoN Er Al. 2,084,177

ELECTRIC POWER SYSTEM Filed Feb. 29, 1936 3 Sheets-Sheet 5 L Inventors z Ernest Fi W. Alexahderson,

Albert, H. Mittag,

Theil" Attorn e5- Plantea June is, 1937 UNITED ySTATESI PATENT lorrlcr.

ELECTRIC PowEa SYSTEM Ems E. w. nemmeno and Albert n. Mittag, Schenectady, N. Y., assignorsto General Electric Company, a corporation of New York Application February 29, 1936, Serial No. 66,434

as claims. (ci. 1ra-s) Our invention relates to electric power systems and more particularly to systems involving the control of motors of the alternating current type through electronic means.

In order to illustrate our invention, we will describe suitable apparatus and methods of operation the l tric ship propulsion system. Our invention is especially useful wherein the motor or motors 10 constitute substantially the sole load for an alternatng current generator and where the motors are required to reverse under load or etect reversal under. certain conditions of operation where the driven member overdrlves the motor.

5 It is, of course, understood, however, that the scope of ourI invention is not limited to the par-- ticular application described but is of general application wherever it is desired to control the speed and direction of rotation of a motor or a 20 plurality oi motors for operating any vessel, locomotive, vehicle or other apparatus.A

It is an object of our invention to provide a new and improved electric power system and method of operation thereof for controlling the speed and direction of rotation o! electric motors.`

It is another object of our inventionl to provide a new and improved electric power system comprising an alternating current generator-,and a motor of the alternating current type wherein the 30 speed of the motor can be varied throughout its operating range with the most eillcieit mode of operation at all times.

It is another object offour invention to-provide a new and improved electricI power system for obtaining control of a motor of the synchronous or induction type over the complete speed range of the motor from a source oi'VA alternating current of selectively variable rangesoi constant irequency.

It is another object of our invention to provide a new and improved electric power system and method of operation thereof wherein motors of the alternating current type are controlled in speed and direction oi.' rotation by electronic means.

In the development of electric ship propulsion systems the essential problem of providing a variable speed ratio between the motor and the generator vwas arri'ved at in various waysf-z'Phe ilrst 50 electrically propelled ship was operated by direct current. The next ship had an alternating current generator and an induction motor with slip rings, so that vspeed control was produced by a variable secondary resistance. One of thelater 55 ships, a battleship, employed a double squirrel for carrying it into effect in an eleccage induction motor and obtained variable speed characteristics with a pole changing winding on theinduction motor. On still other ships synchronous motor systems were employed which could operate as induction motors for reversing and starting but the variable speed characteristics of the induction motor was sacrificed along with the advantage of operating the generator turbines at their most eillcient of the desired speed of the ship.

It is a further object of our invention to provide a new and improved electric power system and method of operation thereof for ship propulsion which combines the complete variability of the speed found in the direct current drives with the economy of synchronous motor design and which gives a flexibility of control much greater 'than with the induction motor systems.

It is va still further object of our invention to provide a new and improved electric power system for ships wherein all maneuvering and reversing is controlled by control circuits of electronic devices thereby eliminating cumbersome and expensive switching in the high power circuits.

In carrying our invention into effect we employ an alternating current generator of standard design, operated at constant speed for each given range or control by a suitable selectively variable constant speed prime mover and connected through controlled electronic means to energize a pair of motors each having a structural resemblance to the synchronous motor. The electronic means for each motor acts as a recti- Ailer with an output which appears in the form o! direct current, and it also serves to guide the direct current successively through different phase windings of its associated motor to produce a torque to rotate the rotor ot the associated motor. Control circuits are provided for each electronic means so that by proper energization of the control circuits the motors may be started from rest and accelerated to their maximum speed in a forward direction, or reversed without changing the direction of current flow in the ileld or armature. windings of the motor. Speed control of the motors is effected by the control circuits of the electronic means and vby variation in the alternator ileld. In the arrangement to be described a pair of control circuits for the elecspeed regardless tronic means are controlled in accordance with the alternator voltage through a phase shifter and maximum power when operated at 24 knots.`

Such` a ship whether itv be a merchant ship or v war ship is apt to be operated at the 30 knot speed only-exceptionally, whereas the normal operating speed will be 24 knots or less. By use of the 'dual system of control it is. therefore, possible to design the electronic equipment for a maximum power of only one-half of the maximum power' of the ship. Such a ship may advantageously be equipped with two independent power plants including boilers, turbines and` generators. For operating the ship at its maximum speedboth generators may be connected to energize the motors directly. When the ship is operated at 24 knots one of these power plants may be shut down and theother power `plant maybe used at its full speed with its maximum power and efficiency for driving the ship at 24 knots. is made possible by the interposition of the electronic system which changes the speed ratio between the generator and the motor, whereas the same power plant would not be capable of driving the ship at- 24 knots witha synchronous connection. i Therefore, the ship would have.to be operated at further reduced power and reduced efilciency because of the necessity of slowing down the power plant.V

Further economy may again result from maintaining the power plant at its normal speed-because during a long cruise it may be possible to shut down the less eilicient auxiliary power plant and derive all the necessary power for operating the ship from the main plant.

We also show and describe means whereby` one of the two electronic equipments may be 'make necessary repairs.

used for serving both propulsion motors. In a propulsion system of the type we describe, this arrangement would be used at lower cruising speeds when one oi' the electronic equipments is sumcient to operate the ship. This arrangement also saves wear and tear on the other equipment which is not needed and leaves either one free as a spare and makes it possible to system, and Fig. 2a and Fig. 2b are,`respectively,

a .ilrst and second section of a diagrammatic illustration of one form of one unit of the system shown in Fig. l.

InFig. 1 of the drawings we have diagrammatically shown a general assembly of the apparatus and electrical connections for carrying out our invention in a two-motor ship propulsion' system with a pair of propellor motors. The electrical circuits are shown in one-line nism for the respective motors.

diagram where possible inl order to simplify the drawings and to aid in making a readily understood disclosure of the apparatus and method of operation of the system. It will, of course, be understood that the operating switches and control apparatusin general oi' our improved system of propulsion is only diagrammatically illustrated in the accompanying drawings and hence is represented in very elementary forms and described by elementary terms. 'I'he system includesa turbo-generator `set 'comprising an alternator I0 and a steam `-or elastic fluid tur-4 y ranged for connection to the supply bus by a switch I0". The alternator l0 may be any suit- I able type and is diagrammatically shown as bein`g oi' the three-phase revolving eld type with a field winding I2 energized by an exciter Il having means illustrated as a rheostat I4 for controlling the excitation of the exciter and thereby the excitation of the alternator I0. Switches lip and lis are connected in` parallel in circuit with the ileld winding of exciter I3 and may be interlocked as shown with the speed control mecha- The alternator i0 is connected through a switch I6 to energize a bus I6. Two motors Ilp and I 'ls-are provided for operating the propellers lip and |83 of the ship. 'The letters p and s are used by way of illustration for indicating the port and starboard motors, respectively, and similar identifying letters will be used in Fig. 1 for the various main circuits and control circuits corresponding to the motor with which it is normally used. The motors Hp and I 1s are illustrated as of the synchronous type. I'he motor i'lp comprises twov armature windings Isp and 20p each comprising phase windings connected in three phase Y-connection with a ileld or exciting winding Zip. In accordance with the broader aspects of our invention the motor may be of the series or shunt type. By way of illustration we have shown the fleld winding 2Ip connected for self excitation of the series type through a switch 22p which is arranged to close the circuit between neutrals of the armature windings in one position and in another position is arranged to connect the fleld winding for excitation from a separate source of excitation 23. I'he source 23 is illustrated as an exciter having a regulating resistance 24 in its vfield circuit. A common operatingmeans indicated by the lever 2B may be arranged as shown for simultaneously controlling the resistors il and Il. Each of the termi- `nals of the armature windings lOp and Zlp is connected tothe proper phase conductor of the bus I l through a phase reversing switch 28p for forward or reverse direction of rotation oi the motors when operated directly from the alternator. Each of the terminals of the armature winding ip and 20p is also interconnected with eachrof the phase conductors of an alternator bus 21p through switch means 28p and electronic means comprising two groups of opposltely connected main power tubes 29p31p and liplip. Switching mechanism 41p is provided to disconnect the motor from the tube circuit and connect the motor directly to the lalternator when desired. The output side of the group of tubes lip-41p is connected to the upper side of 7.

switch 41p by conductors p and the input side Vof the group of tubes Sip-46p is connected to description of Figs. 2a and 2b. The power tubes may be controlled directly by suitable excitation circuits for a pair of electrodes within the 'power tubes as described and claimed in an application of E. F. W. Alexanderson, Serial No. 66,432 or by double control member trigger tubes or dual trigger tubes as described and claimed in an application of E. F. W. Alexanderson, Serial No. 66,433, both flied concurrently herewith and both assigned to the assignee of this application. Further features of `the-control circuits for the power tubes as described and claimed in an application of J. H. Foley, Serial No. 66,380 filed concurrently herewith and assigned to the assignee of this application may be used without departing from our invention in its broader aspects. By way of illustration we have shown a control circuit for the main power tubes which is described and broadly claimed in an application of A. H. Mittag, Serial No. 66,390, filed concurrently herewith and assigned tc the assignee of this application. Each of the main power tubes is illustrated as of the immersion ignitor type and each tube of the group 2911-311 is provided with a control member 50p and each tube of the group 3813-4617 is provided with a control member Sip. Each of the control members 50p and 5ip is provided with an excitation circuit the energization of which is controlled by a control circuit designated as SZp-Gp. for the group of'tubes 29p--31pand 'Sip-69p forv the group of ltubes Sap-48p. Each` of the control circuits of each group of Amain power tubes includes a control or trigger tube 19p and Hp respectively which may likewise be any of the several types well known in the art but we have shown by way of example a mercury vapor type of tube yprovided with an `anode, a heated cathode and a pair of control electrodes or grids. Each ofthe tubes 19p of the control circuits 52p--60p is provided with control grids 12p and-13p and each of the tubes Hp of the control circuits Sip-69p is provided with control 'grids 14p and 15p. A suitable source of excitation 16 indicated as a motor generator set with an alternating current generator is provided for 'energizing the filament or heating .means for the cathodes of the trigger tubes through switches 11 andll respectively. The grids 12p and Hp -are -controlled in accordance with an operating condition of the motor such as the counter E. M. F. of the motor through tap changing phase shifting transformer 19p, a rotaryphase shifting means 19'p both arranged for shifting the phase of the grid potentials of the control tubes for reserve operation of the motor. In certain, cases it will occur to those skilled in the art that the phase shifter 19' may be omitted and the tap phase shifter provided with a plurality of steps of smaller angular shiftper step without departing from our invention in its broader aspects. The gridsllp and 14p are connected through a transformer I with reversed secondary windings for firing the tubes designated up and 11p 180 spart. The grids up and 15p are controlled in accordance with a function of the alternator voltage and are connected through a phase shifting means lip, and transformer Ii'p to the alternator bus 21p through conductors 82p in order to control the several tubes for various speed conditions of the motor. In order to eiect control particularly under starting and slow speed conditions there is also ineluded in circuit with the grids 13p and 15p a distributor mechanism 83p for properly selecting the tube to be conductive in order to di rect the current through the proper phase winding of the motor. This distributor mechanism 83p may be of any suitable form, for example, of the magnetic type such as is shown in United States Letters Patent No. 1,939,437, grantedvDecember 12, 1933 or No. 1,971,188, granted August 21, 1934 or of the mechanical type. In accordance with the broader aspects of our invention,

we utilize a control voltage varying in accordance with the speed and mechanical phase position of the rotor. We have shown, by way of illustration', a rotating segment and brush type of distributor mechanism driven vfrom the motor and comprising a rotating segment member having a conducting segment 84p and anon-conducting segment 85p with a plurality oi cooperating brushes N11-Sip. A common brush and collector Bl'p is connected to the conduct- .ing segment 8l. The brushes are indicated as being/'mounted in a brush rigging 92p in order to, permitshift'ing of the brushes and thereby a shift inthe excitation of the tubes which we refer to as" a shift in motor phase.4 The phase shifting means 'lilp may be arranged to be operated simultaneously with the brush rigging 92p by a common operating means 92'p so that regardless of whether the distributor is short circuited or not, phase shift of the control voltage dependent on the operatingconditionof the motor may be obtained. Thus if the counter E. M. F. is too low for control, the shift of the brush rigging will effect gradual control after a step change has been taken with the tap changer 19p while-1f the distributor is short circuited at an intermediate speed, phase -control o f the motor control voltage is eiected after the step change by the phase shifter 19'p. For one direction of rotation of the associated motor the order of energization of the respective brushes must be in a given sequence and@ for a reverse torque the order of energizationof the brushes is in the same sequence but shifted in phase relative to the mechanical phase position of the rotor. When the distributor reverses then the sequence is reversed by the distributor. A switch 93p for shifting the time of energization of the respective brushes is arranged for simultaneous operation with the phase adjusting transformer 19p by means of a suitable operating means illustrated as a manually operated handle 94p reverse. In circuit with the switch 93p is switching means 95p for short circuiting or removing the distributor mechanism 83p from the grid control circuit, if desired, wher the motor attains a predetermined speed. It is to be understood, however. that the motor may be operated throughout its full s d range under distributor control. The swit g means -p is illustrated a'sbeing operated to its short circuiting position after a certain phase shift has beenr attained withst'he phase shifter tip by means of a common operating means i1- lustrated as a manually operated handlel lip designated speed.

The other unit of our system is illustrated with apparatus designated by way of illustration as the starboard unit and is arranged in the same manner as the port unit so thatcorresponding elements have been designated with like numerals but characterized bythe subscript s.

In accordance with our invention we provide means for obtaining dual operation of the motor by either the port or starboard electronic means and have shown switching means Il for effecting a proper connection of the respective phase terminals of the two motors for this operation. As shown corresponding windings oi' the respective motors are connected in parallel on the output side of one group of tubes and the remaining corresponding windings are connected in parallel on the input side of the return tubes. By closing switch l1 and opening the terminal connections of either motor by switches p and Ils the remaining motor may be operated from the tube control means of the other motor. In other words the port and starboard motors may be operated simultaneously by either the port or starboard` electronic ymeans and either the port or starboard motor may be operated by either the port or starboard electronic means by proper positioning of the switches and by disconnecting one motor-from the circuit. The motors may also be connected for parallel operation directly from the alternator bus I6 through the phase reversing switches 26p and 26s and the switches 41p and 41s so that operation may be obtainedy in the reverse direction as well as the forward direction when energized directly from the alternator.

The operation of the arrangement shown in Fig. l will be explained rst in order to point out with more clarity the various features of operation and the functions of the various control elements and their relation in thecomplete system. For purposes of explaining our invention we will assume the ship propulsion system is of the )rindl having motors l'lp and Ils respectively coupled to port and starboard propellers and where the motors are arranged to be energized from the same generator. With all of the switches in the open position as shown it will be `necessary to close switches 28, 41 to its upper position for tube operation, 11 and 'il for the heater circuit of the control tubes and I3 for the'distributar. bmsnes. with the double grid triggr tube control system as shown the operation for forward speed may be eifected by the operating lever 96 marked Speed' for both port and starboard motors. The speed" lever has an operating position where the alternator eld I2 is open circuited and the whole system is deenrgized.

. The first control position of lever li gives mini- 8l which gives current so low that it is insul- 'cient to st'art the motor. Advancing the'lever It mum alternator excitation and a phase retardation on the grids 13 and 'l5 through phase shifter advances the phase of the potential of gridsl and 'I5 until the full power which is possible with minimum alternator ileld is delivered to the -motor. Further advance of the lever maybe ar ranged to increase the excitation of the alternator ileld by decreasing 'the resistance Il of exciter Il. As the lever I is advanced the distributor` mechanism is short circulted by the switch II so that control is shifted to control in accordance Iwith the counter E. M. F. of the motor andthe phase control of the alternator voltage through phase Il. When this point in the control is obfrom the relatively low intermediate speed to a higher intermediate speed under control of the electronic means in accordance with the phase shift of the alternator voltage and counter E. M. F. of the motor, and third, in accordance with the voltage of the alternator.

Nowlet it be assumed that it is desired to reverse the propeller while the ship is going forward. Since the water drives the propeller as a turbine it is necessary for the motor to exert considerable torque in order to stop the propeller and also to maintain ahigh torque during the whole process of reversal. In accordance with our system the reversal is effected by control of the electronic means without switching in the main power circuits. The direction of curren't flow in the field and armature windings of the illustrated arrangement is not changed for either direction of rotation of the motor. 'I'he reverse" control lever 94 in its first movement for reverse operation shifts the phase of the voltage applied to the grids 12 and 14 through switch 80 so that the time of firing of the several valves of the groups 29-31 and 38-46 is changed to cause the successive energization of the several phase windings of the motor to occur at a time relative to the mechanical position oi' the rotor so that the torque of the motor is reversed. At this point in the reversing cycle while the rotor is being overdriven, the motor begins to act as a series generator with a low negative resistance characteristic. By the term negative resistance characteristic or equivalent negative resistance" we define any circuit element in which a positive increment of current is accompanied by a negative increment of voltage.

Ii we were to have a complete analogy with direct current machinery we would have to imagine a series generator which could be controlled by brush shifting and the circuit completed by another direct current machine corresponding to the alternator which could be controlled by brush shifting. A direct current series generator is usually thought of as an unstable and uncontrollable machine. This is because it acts like a negative resistance. It is, however, known that a series generator becomes a controllable and useful machine if the circuit includes enough positive resistance to odset the negative resistance characteristic of the generator. Shifting the grid phase of the motor by means of the brush shifter 92 controls the amount of equivalent negative resistance of the 'electronic motor and shifting the phase of the control potential dependent upon the generator voltage by means of phase shifter 8i controls the resistance of the output circuit. 'Ihe electronic motor of our system thus possessescharacteristics of controllability especially adapted for ship propulsion. 'Ihe equivalent negative resistance of our motor at the first reverse position Just beyond neutral may be so low that the motor does not self-excite as a series generator. therefore the current must be forced through it by the alternator. This current ilow is controlled by the alternator.. neld I2 and the alternator voltage grid control phase shifter 8|. When the brush yoke 92 is moved further in the direction for the reverse operation the grid excitation of the motor voltage is shifted further until the motor begins to self-excite as-a series generator and increases its 'torque to the desired degree. This in turn will cause the propeller speed to break down which requires still further shift of the motor phase by the brush yoke 92 to maintain series generator operation until the propeller has been brought to standstill and the phase of the control grids of the electronic means adjusted for motor operation in the reverse direction. For further increasing the torque the power must come from the turbo alternator. 'I'he excitation of iield winding I2 must be increased and the phase shifter 8| advanced until the full reversing speed has been reached. Since the brush yoke 92 and the rotary phase shifter 19' may be interlinked as previously suggested and as shown in the drawings any reference to movement of the brush yoke 92 in the method of operation just.described, also applies to the rotary phase shifter 19' when the speed of the motor is sufiicient to have suiicient counter E. M. F. for control.

In Figs. 2a and 2b we have shown, a diagrammatic illustration of a three phase arrangement of one unit of our system shown in Fig. 1. Elements and circuits corresponding to the same elements or circuits in Fig. 1 have been given like reference numerals for ease of identification. The three phase alternator i which is driven by the prime mover II is connected to energize the bus I6. The arrangement is such that the motor I1 may be energized through the electronic means or directly-frorn the alternator. Thus, the bus I6 is connected through the switch 28 to energize the three phase bus 21 for connecting the electronic means to the alternator and through the phase reversal switch 25 to one side of the selective switch 41. 'I'he selectiveswitch 4 1 in its upper position as viewed in the drawings connects the motor windings to the electronic means and in its lower position connects the motor windings in parallelv forv energization directly from the alternator. The motor windings I9 are further identified in Fig. 2b by assigning'letters a, b and c to the respective winding sections or phase windings. Similarly, the-corresponding phase windings of motor windings 20 are indicated by the letters e, f and g. The respective phase termimals of the motor winding I9 are connected through the switch 41 in its upper portion through conductors 48 to the output or cathode terminals of electronic means illustrated as a plurality of single-arc-path electronic valves 29-31 inclusive. These valves in groups of three are connected with their input or anode terminals to the respective phase conductors of the bus 21. The.

respective phase terminals of the motor winding 20 are connected through the switch 41 and conductors 49 to the input or anode terminals of electronic valves 38-46 inclusive. These valves in groups of three are oppositeiy disposed relative t) the first mentionedgroups of valves with respect. to the phase conductors of bus 21 since the cathode terminals are connected to the bus 21. The electronic means are preferably of the gaseousor vapor type and may be of the multiple the tank type rectifier or the single anode-singlecathode Ytype with'a heated cathode or a pool type cathode. We

have illustrated` by way of example single arc path electronic valves of the immersion ignltor type and each valve of the groups 29-31 and 38--46 is provided with .an anode, a pool type cathode and a control member or electrode 50 and 5I respectively. The three groups of valves 29-3|, 32-34, and 35-31 operate as controlled rectiiiers to supply unidirectional current to the motor windings I9. The three groups of oppositely disposed valves 38-40, 4I-43, and 44-46 operate as controlled rectiers to return the unldirectional current to the bus 21 through the field winding 2|' and motor windings 20. The sequence of energizationof the phase windings of the motor is controlled by controlling the energization of the various groups of valves associated with the respective phase windings.

In accordance with this particular embodiment of .our invention we provide individual control circuits 52-89 for the valves 29-46 respectively. The control circuit 52 for valve 29 and the control circuit 6| for valve 38 are shown in detail, and identical control circuits for the remaining valves are represented schematically by a rectangular outline with connections indicated in the proper manner and sequence corresponding to the valve to be controlled. It is believed that this part of our invention will be readily understood by an explanation in detail of control circuit 52.

The control circuit 52 for valve 29 comprises an electronic device 10 preferably of the gaseous or vapor type valve having an anode, a cathode and the control members 12 and 13. Means responsive to a condition of the supply circuit and the motor circuit is provided for conjointly controlling the conductivity of valve 10. 'I'he control member 13 is energized in acordance With a condition ofthe supply circuit through a transformer |00 having a primary winding I0| and a secondary winding |02. The transformer |00 is energized from the valve supply bus 21 through the rotary phase shifting means 8| and a transformer 8|. The secondary winding of transformer 8|' comprises a double three phase arrangement of windings I03-I08. One terminal of each primary winding I0| of the transformers |00 for the control circuits for valves 29 to 31 is connected to the terminals of windings |03, |05, and |01 through conductors 3, 5, and 1 respectively, and each of the corresponding transformer terminals for the control units of the oppositely disposed group of valves 38 to 46 is eneris connected to the rotor `of the motor I1. The

distributor 83 is provided with a brush 84.' which is connected to the neutral connection of the secondary winding of transformer 8|. The distributor comprises a non-conducting segment 85,

' shown in black, and a conducting segment 84 of 120 electrical degrees and brushes 869| which are displaced by sixty electrical degrees relative to each other. The brushes 81, 89, and 9| are connected in a circuit with the transformer |00 through conductors 81', 89', and 9|' respectively,

for the valves 29 to 31 and through the phase shifting switch 93 for initiating the reversing cycle of operation for the motor.- Similarly the brushes 86, 88, and 90 are connected in a circuitwith the transformer |00 through conductors 86', 88', and 90' respectively, for the valves 38 to 46 and through thephase shifting switch 93. The switch 95 is connected to the conductors from the several brushes in order that the distributor may be removed from the circuit or as shown short'circontrol electrode 12.

cuited when it is desired to effect control of the motor in accordance with the counter E. M. F. of the motor. To prevent interchange of energy between the several grid circuits of the` grids 13 for the group of valves associated therewith when a distributor is used having-a plurality of grid circuits connected to the same circuits, a rectifier |09 is connected in series relation with the primary winding of transformer I 00.

A' voltage which varies in accordance with a condition of the motor is impressed on the control member 12 through transformer H0 having a primary winding III and two secondary windings H2 and H3. A bi-phase rectifying unit I |4 comprising a transformer H5 having a primary winding H6 and a secondary winding H1, unidirectional conducting devices H8, a smoothing inductance H9, and a resistance |20, is provided to furnish a negative bias in the circuit of on transformer H5 furnishes heating current for the valve 10. -The left hand terminal of transformer winding |02 is connected to the cathode of valve 10 and to the control electrode 50 of valve 29. The anode of valve '10 is connected through current limiting means such as the fuse |22 and resistor |23 to the anode of valve 29. The valve 10 is thus energized in accordance with the voltage appearing across the anode and cathode of the main valve 29. The transformer H0 is connected to be energized in accordance with the voltage of the motor I1 and is connected through the phase adjusting transformer 19 which is provided on the secondary winding side with a switch 90 for effecting a proper shift in the phase of the voltages energizing the transformer I I0 when the motor is increased under counter E. M. F. control. The heater circuits of the control valves for the excitation circuits 52-90 is obtained from the separate source of excitation 16 through conductors 18'. Similarly the heater circuits for the excitation circuits 9 |-99 is obtained from the source 16 through conductors 11'.

The operation of the illustrated embodiment ofone unit of our system as shown in Figs. 2a and 2b is substantially as follows: The general principles of operation of the motor through the valves has been pointed out previously in connection with the description of Fig. A1. It will be assumed that the prime mover is operating the alternator with minimum field excitation, that switch 28 is closed, that switch 41 is closed to its upper or valve" position, that switch 93 is closed to its lower or forward position, that switch 95 is in its open position for distributor operation, that switch 22 is in its left-hand position to connect the neutrals of the motor windings through the field winding 2|, and that the rotor is in approximately the position illustrated. It will also be assumed that the rotary phase shifting transformer 8| is adjusted so that the phase of the alternating potential impressed on the control electrodes 13 andv 15 of the valves 10 and 1| will be retarded with respect to the anode potentials in order to reduce the average voltage impressed on the windings |9 and 20 of motor |1. Under the assumed conditions the brushes 89 and 99 of the distributor 83 are connected through the conductive segment 84, so that the excitation control transformer |00 of the group of valves 32-94, and 44 to 48 are energized respectively. These two groups of valves now act as lcontrolled rectiers supplying uni- A secondary winding I 2|- directional current to |9b from the valves 32-34, through field winding 2|, and then through 20g and back to the supply bus through valves 44-49. It will be assumed that with these portions of the armature winding energized their magnetomotive force will produce a torque upon the rotor 2| to accelerate it in a clockwise direction. When the rotor has turned through substantially 90 electrical degrees the conductive segment of the distributor interrupts the circuit from brush 89, maintains the circuit for brush 90 and establishes a circuit for brush 9|. The closing of the circuit of brush 9| establishes the excitation circuit of the groups of valves 29 to 3|. With this excitation circuit energized current is transferred from |9b to |9a advancing the phase of the magnetomotive force of the motor by electrical degrees so that the rotor is again in approximately maximum torque producing position with respect to the motor-magnetomotive force. In this manner the current is successively transferred between the several terminals of the armature windings |9 and 20 to produce a rotation of the rotating member 2|. With the arrangement described it will be noted that under anytransformer 8|.

The operation just described is one method of controlling the motor at; starting andfor relatively low speeds. In this case the rectified current is directed through the respective phase windings of the motor in accordance with the mechanical phase position of the rotor. Satisfactory operation of the motor above approximately half speed may be obtained by effecting control of the trigger valves and therefore of the main valves in accordance with the counter E. M. F. of the armature windings. vThe trigger valves 10 and- 1| are constructed-.fand arranged so that either of the control members may maintain the valve non-conductive by impressing a voltage sumciently negative in polarity on the control members. The valves, however, may be rendered conductive if suitable voltages are impressed concurrently on both control members. In the low speed range the counter E. M. F. may be insufficient to render the valves non-conductive but the generator voltage through the distributor is sumcient to effect the desired control. When the motor is up to say half-speed the distributor is disconnected vfrom the circuit by closing the switch 95, and the grids 12 are then suiilciently energized by the counter E. M. F. of the motor to co-operate with the generator voltage on the grids 13 to obtain proper firing of the main valves so as to energize the motor windings in the proper sequence for further acceleration to full speed forward.

For obtaining reverse rotation of the motor, the phase shifting switch 93 is moved to its upper position and the phase shifting switch 90 is moved to its lower position. With this change in the switching the motor is reversed in accordance with the general principles of operation set forth in the description of Fig. 1. If in the forward direction of rotation of the motor we assume the stator M. M. F. is in advance of the rotor M. M. F. then when the phase shift switch 93 is verse direction the phase rotation of the motor windings is reversed by reason of the reverse rotation of the distributor which selects the particular valves for energization and controls the sequence of energization of the motor windings for operating the motor in the reverse direction. In view ofthe previous description of the general features of the operation of the motor in the reverse direction coupled with the detailed description of the operation oi.' the motor in the forwarddirection, it is believed it will not be necessary for a clear understanding of our invention to describe. further details of the operation of the motor for the reverse rotation.

While we have shown and described a particular embodiment of our invention, it will .be obvious to those skilled in the art that various changes and modiiications may be made without departing from our invention in its broader aspects and we, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention. l l

What we claim as new and desire to secure by Letters Patent of the United States is: l

l. In an electric power system, a generator,

a motor having armature and iield windings, and l electronic means including a plurality of 'discharge paths and constructed and arranged for causing operation oi' said motor from one direc-l tion of rotationto another with the same relative direction of current flow in said armature and iield windings, said electronic means including means arranged to change the time of energization of the respective discharge paths without changingthe sequence of energization of said discharge paths prior to reversal of direction of rotation of said motor.

2. In an electric power system, a generator, a motor having armature and held windings, a member coupled to be driven by said motor under certain conditions of operation and overdriving said motor'under certain other conditions of operation, and electronic means constructed and arranged for causing operation of said motor in either direction of rotation with the same direction of current flow in said armature and iield windings.

3. In an electric power system, an alternating current generator, a motor of the alternating current type having a stator winding comprising a plurality of winding sections and a rotor winding connected to be energized in series relation with said winding sections, and electronic means including a plurality of discharge paths and constructed and arranged for causing operation of said motor from one direction 'of rotation to another with the same relative direction of current iiow in said stator and rotor windings, said electronic means including means arranged to change the time of energization of the respective discharge paths without changing the sequence oif-energization of said discharge paths prior tuv reversal of direction of rotation oi.' said motor. 4. In anrelectric Ypower system, an alternating current generator,` a motor of the alternating current type having a stator winding comprising a plurality of winding sections and a rotor winding connected to be energized in series relation with said winding sections, a member coupled to be driven by said motor under certain conditions of operation and overdriving said motor under Vcertain other conditionsof operation, and electronic means constructed and arranged for causing operation of said motor in either direction of rotation with the same relative direction of current iiow in said stator and rotor windings.

5. In an electric ship propulsion system comprising-in combination a prime mover, a synchronous generator coupled to said prime mover, a propeller, a motor of the synchronous'type having statorl and rotor windings and coupled to s said propeller, and electronic means including a plurality of discharge paths and constructed and arranged for causing operation of said motor from one direction of rotation to another with the same vdirection oi' current iiow in said stator and rotor windings, said electronic means including means arranged to change the time of energization of the respective discharge paths without changing the sequence of energization of said discharge paths prior to reversal of direction oi' rotation of said motor.

6. In an electric power system, an alternating current generator, a motor of the alternating current type including a rotating iield member, means connected between said generator and said motor comprising electronic means having a plurality of discharge paths, means for controlling the conductivity of said discharge paths, means ior controlling the sequence of energization of the conductivity controlling means, and means for effecting reversal of thetorque of said motor comprising means for shifting with the" same sequence the time ofenergization of the conductivity controlling means relative to the angular position of said field member while said iield member is rotating in a direction lopposite to the direction of torque of said motor.

'Il In an electric power system, an alternating current generator, a motor of the alternating current'type including a rotating iield member, i

means connected between said generator and said l motor comprising electronic means having a plurality of discharge paths, means for controlling the initiation of the discharge in the severaldischarge paths, means connected to said field member for determining the sequence of energization of the discharge initiation means, and means for effecting a reversal of the torque of said motor and consequent reversal in directionof rotation' control members, a distributor driven by said` motor to excite said control members in a predetermined'sequence, and means for selectively determining the time of energization ot said control members relative to the angular position oi' said ileld member for controlling the direction of torque of said motor.

9. An electric power system comprising a source of current, a polyphase motor provided with aplurality of phase terminals and with a rotating ileldmember, a plurality of electric valves interconnecting said source and said terminals, each of said valves being provided with a control member, a source of potential for energizing said control members, a distributor coupled to said motor and interconnecting said source of potential and said control members to excite said control members 4in a predetermined sequence, and switching ing a plurality of discharge paths, and means arranged to control conJointly the sequence and time of conductivity of the respective discharge paths for controlling the said motor. r`

11. In an electric ship propulsion system comprising in combination a prime mover, an alternating current generator coupled to said prime mover, a propeller, a motor coupled to said propeller and having a rotating field member, means direction of rotation of connected between said generator and said motor comprising electronic means having a plurality bf discharge paths, means operative in accordance with an operating condition of said motor for controlling the sequence of conductivity of the respective discharge paths, and means for selectively determining the time of energization of said discharge paths relative to the angular position of said rotating l:lield member for reversing the direction of torque of said motor while the direction of rotation oi' said motor is opposite to said torque.

12. In an electric ship propulsion system comprising ifi combination an elastic iluid turbine. an alternating current generator coupled to said turbine, a propeller, a motor of thealternating current type coupled to said propeller, means connected between said generator and said motor and comprising electronic means having a plurality of discharge paths, said electronic means having a control member for each discharge path for selectively initiating current ilow in the respective discharge paths, and means arranged to control conjointly the sequence and the time of energization of said control members for controlling the direction of rotation of said motor.

13. In an electric power system, an alternating current generator, a motor of the alternating current type having a stator winding comprising a plurality of winding sections and a rotor winding connected to be energized in sexies relation with said winding sections, a member coupled to be driven by said motor under certain conditions of operation and overdriving said motor under certain other conditions oi' operation, "electronic means having a plurality of discharge paths.' a discharge path being included in series vrelation i nating current type, electronic means for controlling the energization of said motor, means arranged to control said electronic means for controlling the phase rotation of said motor, and means for selectively determining the direction of the torque of said motor for any given phase rotation thereof.

15. The method of reversing a ship while in motion with a ship propulsion system including an alternating. current generator, a propeller, a motor oi' the alternating current type comprising armature and ileld windings, and electronic means interposed between said generator and said motor which comprises controlling said electronic means to shift the armature iluxv relative vto the neld flux of said motor in a direction to reverse the torque oi' the motor, further controlling said electronic means so 'that said motor operates as a generator,

still vfurther controlling' said electronic means until saidv motor cames to rest, and then reversing the phase rotation of saidmotor and controlling 16. The method oi'freversing a ship while in motion with aship propulsion system including a prime mover, a variable voltage alternating current generator driven thereby, a propeller, a motor of the synchronous type comprising a stator with a plurality oi' winding sections thereon and a rotor with a winding in series relation with said. sections, and controlled electronic ysaid electronicmeans for operatingsaid motor in the reverse directiomx means interposed in series relation between said generator and motor, which comprises sluiting the stator flux relative to the rotor ux by said electronic means in a direction to reverse the torque of said motor, then controlling the current ilow through said motor by varying the voltage of the generator and varying the time of initiation of the discharge in said electronic means until said motor begins to self-excite as a series generator, then still varying the time of initiation of the discharge in said electronic means until said propeller is brought to rest'and the time of initiation oi'the discharge is such that said motor is energized for motor operation in the reverse direction, and then further changing the time oi' initiation of the discharge of the electronic means and thevoltage of the alternator until full reversing speed has been attained.

17; The method of reversing an overdriven' electric motor in an electric power system comprising a variable voltage alternating current generator connected to energize through controlledelectronic means an electric motor of the synchronous type having a ileld winding in series relation with the armature winding which cornprises shifting the phase of the armature M. M. F. relative to the ileld M. M; F. by the electronic means in a direction to reverse the torque of the motor, then controlling the current dow through said motor by varying the voltage of the generator and varying the time of initiation of the dis- `i'rom either electronic means.`

begins to self-excite as a series generator, then still varying the time of initiation of the discharge in said electronic means until said motor is brought to rest andthe time of initiation of the discharge is such as to obtainmotor operation in the reverse direction, and then iurther changing the time of vinitiation of 'the discharge o! the, electric means and the voltage of the alternator until full reversing speed has been attained.

18. In an electric ship propulsion system, a prime mover, an alternating current generator coupled to said prime mover, an electric motor having a rotor, a propeller coupled to said motor, electronic means comprising a plurality of discharge paths for transmitting current between said generator and said motor, means for changing the time of initiation of current iiow in said discharge paths, distributor means coupled to said motor for. controlling the sequence oi initiation of current ilow in the several discharge pathsv of said electronic means when said motor operates in either direction, and interlocking means for conjointly controlling the means for changing the time of initiation of current flow and said distributor means for effecting a reversal in direction of rotation of said motor.

19, In an electric power system, an alternating current generator, a plurality of motors connected to be energized from said generator, individual electronic means for controlling each motor, and means arranged for selectively controlling any one motor from any one electronic means.

20. In an electric power system,l an alternating current generator, a plurality of motors connectedto be energized fromsaid generator, individual electronic means `for controlling each motor, and means arrangedl for selectively controlling all of said motors from any one oi said electronic means.v

21. The combination in a system of ship propulsion, of a propeller on each side of the ship, a motor coupled to each propeller, ,electronic means for controlling each motor, and means ar- .ranged for selectively controllirgu either motor 22. The combination in a system of ship propulsion of a propeller on each-side of the ship,

a motor coupled to each propeller, electronic means for controlling each motor, and means arranged for selectively controlling the simulta- Y neous operation of both motors from either one of said electronic means.

23. In an electric power system, an alternating current generator, an electric motor,V electronic means arranged for connection in series relation with said motor, and means for selec--l tively energizing said motor through said electronic means or directly from said generator.

24. In van electric ship propulsion system, a pair of power plants each comprising a prime mover and an alternating current generator driven thereby, a propeller, a motor coupled to said propeller, electronic means for at times con` trolling the energization of said motor, means for connecting said motor directly to said gen-v erators for operation of said ship between an intermediate speed and its maximum speed, means for connecting said motor to'one of said generators through said electronic means for operation of said ship at substantially said intermediate speed, and means for connecting said motor directly to one of said generators for operation oi.' said ship lat speeds below said intermediate.

speed.

25. The methodof controlling a ship with a ship propulsion system comprising duplicate power plants each of which includes a prime mover and an alternating currentrgenerator driven thereby, a propeller, a motor, and electronic means for at times controlling thev energization of said motor which comprises energizing said motor direct y from both of the 'generators for operation i said ship for speeds above a predetermined intermediate speed, energizing said motor through said electronic means for operation of said ship at substantially said intermediate speed, and energizing said motor directly from one of said generators for speeds of said ship below said intermediate speed.A

26. In an electric power system, an alternating current generator, means for varying the voltage of said generator, an electric motor, electronicmeans interposed between said generator and said motor, and means for varying the operation of said motor by varying the conductivity of said electronic means and the voltage of said generator.

27. In an electric ship propulsion system, a prime mover, an alternating current generator coupled to said prime mover, an electric motor, a propeller coupled to said motor, electronic means interposed between said generator and said motor, and means for varying the speed of4 the ship by varying both the conductivity of said electronic means and the voltage of said generator.

28. In an electric ship propulsion system, a selectively variable constant speed prime mover, an alternating current generator coupled to said prime mover, an, electric motor, a propeller coupled to said motor, electronic means interposed between said generator and said motor, and means for varying the speed of the ship by varying the' conductivity of said electronic means and the'voltage oi.' said generator for each se'- lected speed of said prime mover.

29. In an, electric ship propulsion system, a prime mover, an alternating current generator coupled to said prime mover, an electric motor,

a propeller coupled to` said motor, electronic means for transmitting current between said generator and said motor, means for varying the conductivity of said electronic means, means for varying the voltage of said generator, and interlocking means for simultaneously operating the conductivity control mean's\and the voltage varying means.

-30. In a ship propulsion system, a prime mover, an alternating current generator coupled to said prime mover, a motor of the synchronous type having a stator and a rotor member, a propeller coupled to said motor, electronic means interposed between said generator and said motor, means for varying the conductivity of said electronic means, and means for controlling the speed of the ship by said iirst-mentioned means in accordance with the mechanical phase posivtion of said rotor.

31. In a ship propulsion system, a prime mover,-

by said tint-mentioned means in accordance with. the counter-electromotive force of the motor.

32. In a ship propulsion system, a prime mover, an alternating current generator coupled to said 5 prime mover, a motor, a propeller coupled to said motor, electronic means interposed between said generator and said motor, and means for controlling the speed of the ship through said electronic means by varying the voltage of said lo generator.

33. In a ship propulsion system, a prime mover, an alternating current generator coupled to said prime mover, a motor of the synchronous type having a stator and a rotor member, a propeller coupled to said motor, electronic means inter- -posed between said generator and said motor, conductivity varying means for said electronic means, means for controlling the speed of the ship from standstill to a relative low intermediate speed by said conductivity varying means in accordance with the mechanical phase position of said rotor, means for` controlling the speed of the ship from relative low intermediate speed to a higher intermediate speed by said conductivity varying means in accordance with the counter-electromotlve force of said motor, and means for controlling the speed of the ship from said higher intermediate speed to its maximum speed through said electronic means by varying the voltage of said generator.

34. The method of controlling the speedA of a ship with a ship propulsion system including a prime mover, a variable voltage alternating current generator driven thereby, apropeller, a

motor of the synchronous type comprising a stator with a plurality of winding sections thereon and a rotor, and electronic means interposed between said generator and said motor which comprises varying the conductivity ofv said electronic means from a. low value of average current. to an inter-s mediate value of average current and successive ly establishing energizatio'nof the several phase windings of said motor from said electronic means in accordance with the angular position 45 of the rotor, then further increasing the conductivity of said electronic means and successively establishing energizatlon of the several phase windings of said motor from said electronic means in accordance with the counter E. M. F.

of said motor, and then when said electronic means is fully conductive increasing the voltage oliisaid generator vfor increasing the speed of said S D. 35. In an electric power system, a source of a1- ternating current, an electric motor havinga rotor member, electric translating apparatus interconnecting said. generator and said motor comprising electronic means having input and output electrodes, control means for said electric means connected to be energized in accordance with the voltage appearing across said electrodes and comprising an electronic device having two control members, means for energizing one of said control members with a voltage varying in accordance with an operating condition of said motor, and means for energizing the other oi.' said control members in accordance with an electrical condition of said source of alternating current.

36. In an electric power system, a source of alternating current, a dynamo-electric machine and an immersion-ignitor control member, andan excitation circuit energized in accordance with the voltage appearing across said anode and said cathode of said electric valve comprising an electronic device of the gaseous type having two control members, a distributor mechanism for said dynamo-electric machine, means for energizing one of said control members through said distributor mechanism in accordance with the angular position .of the M. M. F. of said vrotor relative to the M. M. F. of said stator, and means for energizing the other of said control members in accordance with an electrical condition of said dynamo-electric machine.

37. In combination, an alternating current supply circuit, a dynamo-electric machine of the synchronous type having a plurality of phase windings and a eld winding connected to be energized in series relation with said phase windings, a plurality of electric valves for transmitting current from said supply circuit to said phase windings, a plurality of electric valves disposed in a sense opposite to that of said first-mentioned valves for returning said current through said ileld winding and said phase windings, and a plurality of excitation circuits for effecting selective energization of said phase windings and each being associated with a diierent one of said electric valves and being energized in accordance with the voltage appearing across an anode and cathode of said associated electric valve comprising an electronic discharge device, distributor mechanism coupled to said dynamo-electric machine,

means for controlling the energization of said electronic discharge device through said distributor mechanism from said supply circuit, and means for controlling the energization of said device in accordance with a function of the voltage oi' said machine.

38. In combination, an alternating current supply circuit, a motor of the synchronous type having a plurality of phase windings and a eld Winding connected to be energized in series relalation with said kphase windings, a plurality of electric valves for transmitting current from said supply circuit to said phase windings, a plurality of electric valves disposed in a sense opposite to that of said first-mentioned valves for returning said current through said ileld winding and said phase windings, and a plurality of excitation circuits each associated with a' diierent one of said electric valves and being energized in accordance with the voltageappearing across an anode and cathode of said associated electric valve comprising 'an electronic discharge device having two control members for conjointly controlling the conductivity of said device, means comprising a distributor mechanism coupled to said motor for energizing one of said control members from said supply circuit, and means for energizing the other of said control members in accordance with the C. E. M. F. of said motor.

ERNST F. W. ALEXANDERSON. ALBER'II- H. MII'IAG. 

